JP2001056023A - Spindle motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To certainly prevent leakage of lubricating oil outside of a spindle motor on which a rotor is supported free to rotate on a stator by a fluid dynamic pressure bearing constituted of a shaft with a flange and a one end open type sleeve. SOLUTION: A labyrinth seal part made of disc type small clearance part horizontal toward an outer peripheral part from an inner peripheral part, a vertical ring type small clearance part, a horizontal disc small clearance part and a vertical ring small clearance part near the outer peripheral part sequentially connected and tangled with each other is formed between a back surface of a hub 6 and an upper end surface, of a first sleeve member 4 on a spindle motor where a rotor having the hub 6 is supported free to rotate by the stator by a fluid dynamic pressure bearing constituted of a shaft 1 with a flange formed as a columnar member 2 press-fitted in a ring member 3, a one-end open type sleeve made of the thick first sleeve member 4 and a second sleeve member 5 and lubricating oil filled in a small clearance including a bearing clearance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flanged shaft formed by pressing a cylindrical member into a ring member, a first sleeve member into which the cylindrical member is inserted, and a second sleeve into which the ring member is inserted. A rotor having a hub rotates to a stator by a fluid dynamic pressure bearing composed of a one-end open type sleeve composed of a member and lubricating oil filled in a minute gap including a bearing gap formed between these bearing constituent members. The present invention relates to a freely supported spindle motor, and particularly to a structure for preventing leakage of lubricating oil.

[0002]

2. Description of the Related Art FIG. 7 shows a flanged shaft 1 formed by press-fitting a ring member 3 into a cylindrical member 2, a first sleeve member 4 into which the cylindrical member 2 is inserted, and a first shaft member into which a ring member 3 is inserted. Fluid dynamic bearing composed of an open-ended sleeve composed of two sleeve members 5 and lubricating oil filled in minute gaps R1, R2, R3, R4 including bearing gaps formed between these bearing components. FIG. 7 is a longitudinal sectional view of a conventional spindle motor in which a rotor having a hub 6 is rotatably supported by a stator. The rotor has a hub 6 and a rotor magnet 7 attached to the inner peripheral surface of a skirt 6c. The stator has a stator coil 8 attached to an outer peripheral surface of a cylindrical portion 9a of a motor board 9.

A radial dynamic pressure groove G1 such as a herringbone groove is formed on the outer peripheral surface at the center of the cylindrical member 2.
A thrust dynamic pressure groove such as a spiral herringbone groove is formed on the upper and lower surfaces of the ring member 3.

The inner peripheral surface of the first sleeve member 4 and the cylindrical member 2
The annular minute gap R1 formed between the annular minute gap R1 and the outer peripheral surface of the ring has a lower annular minute gap functioning as a radial bearing gap, and the upper annular minute gap serves as a capillary seal minute gap. It works. A disk-shaped minute gap R2 formed between the upper surface of the ring member 3 and the lower end surface of the first sleeve member 4, and a disk formed between the lower surface of the ring member 3 and the bottom surface of the second sleeve member 5. Each of the small minute gaps R3 is a thrust bearing gap.
The annular minute gap R4 formed between the outer peripheral surface of the ring member 3 and the inner peripheral surface of the cylindrical portion of the second sleeve member 5 functions as a lubricating oil reservoir.

[0005] The first sleeve member 4 is formed with a tapered notch at the upper open end of the inner peripheral surface thereof. Therefore, between this tapered notch and the outer peripheral surface of the columnar member 2, a tapered annular gap S gradually expanding toward the atmosphere is provided.
Are formed. The opposite side of the tapered annular gap S on the atmosphere side communicates with the annular minute gap above the minute gap R1, that is, the minute gap for the capillary seal. The gap portion where the tapered annular gap S opened to the atmosphere and the minute gap for capillary seal of the minute gap R1 communicate with each other functions as a capillary seal.

The capillary seal prevents the lubricating oil filled in the bearing from leaking out of the bearing by the action of capillary action and surface tension, and is widely used in fluid dynamic bearings. . However, in the spindle motor shown in FIG. 7, the length of the capillary seal is not sufficient, and the lubricating oil leaks out of the bearing due to thermal expansion of the lubricating oil, centrifugal force, and capillary action due to fine scratches on the processing surface. was there.

Therefore, a labyrinth seal has been conventionally used for some fluid dynamic bearings and spindle motors instead of or together with the capillary seal. For example, US Pat. No. 5,487,608,
JP-A-7-264796, JP-A-7-33692
No. 4, JP-A-9-264320, JP-A-11-55
No. 898 discloses a labyrinth seal.
However, the labyrinth seals disclosed in these patent publications can be realized only in a fluid dynamic pressure bearing or a spindle motor having a specific structure, and the spindle motor to which the present invention is applied, that is, the cylindrical member is a ring member A shaft with a flange formed by press-fitting, a first sleeve member including a first sleeve member into which the cylindrical member is inserted, and a second sleeve member into which the ring member is inserted, and between these bearing constituent members. It cannot be applied to a spindle motor in which a rotor having a hub is rotatably supported on a stator by a fluid dynamic pressure bearing composed of a lubricating oil filled in a minute gap including a formed bearing gap.

[0008]

The object of the present invention is to provide a flanged shaft formed by press-fitting a cylindrical member into a ring member, a first sleeve member into which the cylindrical member is inserted, and the ring. A fluid dynamic pressure bearing composed of a one-end open type sleeve composed of a second sleeve member into which the member is inserted, and a lubricating oil filled in a minute clearance including a bearing clearance formed between these bearing components, In a spindle motor in which a rotor having a hub is rotatably supported by a stator, it is an object to reliably prevent leakage of lubricating oil to the outside.

[0009]

In order to solve the above problems, a flanged shaft formed by press-fitting a cylindrical member into a ring member, a thick first sleeve member into which the cylindrical member is inserted, and Second where the ring member is inserted
A rotor having a hub is mounted on the stator by a fluid dynamic pressure bearing composed of a one-end open sleeve composed of a sleeve member and lubricating oil filled in a minute clearance including a bearing clearance formed between these bearing components. In the spindle motor rotatably supported, a labyrinth seal portion is formed between a back surface of the hub and an upper end surface of the first sleeve member.

The labyrinth seal portion is formed by a minute gap between the downward annular projection formed on the rear surface of the hub and the upward annular projection formed on the upper end surface of the first sleeve member.

Further, the labyrinth seal portion is constituted by a minute gap between a substantially conical concave portion formed on the back surface of the hub and a substantially conical convex portion formed on the upper end surface of the first sleeve member. . Further, a dynamic pressure groove is formed on the surface of the substantially conical convex portion so that a dynamic pressure is generated from the outside to the inside of the bearing.

Further, the open end of the labyrinth seal portion is tapered so as to function as a capillary seal.

[0013]

FIG. 1 is a longitudinal sectional view of a spindle motor according to an embodiment of the present invention, in which a minute gap is exaggerated. The spindle motor of FIG. 1 includes a flanged shaft 1 formed by press-fitting a ring member 3 into a cylindrical member 2,
An open-ended sleeve composed of a first sleeve member 4 into which the cylindrical member 2 is inserted and a second sleeve member 5 into which the ring member 3 is inserted, and a minute gap R1 including a bearing gap formed between these bearing components. , R2, R3, R4 and the like, and the rotor is rotatably supported by the stator by a fluid dynamic pressure bearing composed of lubricating oil.

The rotor has a hub 6 coaxially fixed to the upper end of the cylindrical member 2 of the flanged shaft 1 and a rotor magnet 7 attached to the inner peripheral surface of the skirt 6c. The stator has a stator coil 8 attached to an outer peripheral surface of a cylindrical portion 9a of a motor board 9.

The shaft 1 with a flange is a member having a shape as shown in the perspective view of FIG. 5, and a radial dynamic pressure groove G1 such as a herringbone groove is formed on the outer peripheral surface of a central portion of the cylindrical member 2.
Are formed. A thrust dynamic pressure groove G2 such as a spiral herringbone groove is formed on the upper and lower surfaces of the ring member 3 of the flanged shaft 1.

An annular minute gap R1 formed between the flat inner peripheral surface of the first sleeve member 4 and the outer peripheral surface of the cylindrical member 2.
In the figure, the lower annular minute gap functions as a radial bearing gap, and the upper annular minute gap functions as a capillary seal minute gap. A disc-shaped minute gap R2 formed between the upper surface of the ring member 3 and the flat lower end surface of the first sleeve member 4, and between the lower surface of the ring member 3 and the flat bottom surface of the second sleeve member 5. Each of the formed disc-shaped minute gaps R3 is a thrust bearing gap. The annular minute gap R4 formed between the outer peripheral surface of the ring member 3 and the inner peripheral surface of the cylindrical portion of the second sleeve member 5 functions as a lubricating oil reservoir. The interval between the minute gaps R1, R2, and R3 is about 10 to 100 μm, and an appropriate gap is selected depending on the size of the bearing, the number of rotations, and the viscosity of the lubricating oil. Further, the interval of the minute gap R4 is selected to be a larger value.

As shown in the perspective view of FIG. 6, the first sleeve member 4 is a substantially cylindrical member having a large outer diameter and a small inner diameter, that is, a thick cylindrical member. The first sleeve member 4 functions as a member for forming a radial bearing gap and a thrust bearing gap, respectively, as described above.
As described in detail below, it also functions as a member forming a labyrinth seal portion.

That is, in the present invention, the upper end surface of the first sleeve member 4 is arranged close to the back surface of the hub 6 at a short interval of about several tens to several hundreds of micrometers. Moreover, the minute gap formed between the upper end surface of the first sleeve member 4 and the back surface of the hub 6 is not a simple disk-shaped gap extending horizontally, but
It is a complicated minute gap having an intricate minute gap or a tapered disk-shaped minute gap inclined in the outer peripheral direction, and forms a so-called labyrinth-like minute gap R5. One end of the labyrinth-like minute gap R5 opens to the atmosphere, and the other end communicates with the minute gap R1. Hereinafter, embodiments of the labyrinth-like minute gap R5 will be described.

The fluid dynamic pressure bearing according to the first embodiment shown in FIG. 2 in which the minute gap is exaggerated is shown. The flanged shaft 1 formed by press-fitting the ring member 3 into the cylindrical member 2 and the cylindrical member 2 are inserted. A sleeve including a first sleeve member 4 and a second sleeve member 5 into which the ring member 3 is inserted, a gap including a bearing gap formed between these bearing components,
That is, the minute gaps R1, R2, R3, R4, R5, the vertical holes r
1, the lubricating oil F filled in the circulation hole r2, the vertical groove r3, and the circulation hole r4.

The flanged shaft 1 is a member having a shape as shown in FIG. 5, and the first sleeve member 4 is a substantially cylindrical member having a thickness as shown in FIG. The second sleeve member 5 is a cylindrical member having both ends open, which also functions as a bearing case. The lower open end is hermetically and liquid-tightly sealed by a disc-shaped lid member 10 to form a one-end open sleeve. Has become. Thus, the upper surface of the disc-shaped lid member 10 forms the bottom surface of the second sleeve member. A plurality of vertical holes r1 and circulation holes r2 formed in the ring member 3;
The plurality of vertical grooves r3 and the circulation holes r4 formed in the sleeve member 4 function as a lubricating oil reservoir and a circulation path.

The minute clearance between the upper end surface of the first sleeve member 4 and the back surface of the hub 6 is not a simple disk-like clearance extending horizontally, but a horizontal disk-like minute clearance from the inner peripheral portion to the outer peripheral portion. A labyrinth-like micro-gap R having an intricate shape in which a gap, a vertical annular micro-gap, a horizontal disk-shaped micro-gap, and a vertical annular micro-gap near the outer periphery are sequentially connected.
5 are formed. One end of the labyrinth-like minute gap R5 is open to the atmosphere, and the other end is communicated with the minute gap R1, but the length between the open end to the atmosphere and the minute gap R1 is for the capillary seal of the minute gap R1. It is sufficiently longer than the length of the minute gap. In FIG. 2, this sufficiently long communication path is realized by forming a downward annular projection 6a on the back surface of the hub 6 and an upward annular projection 4a on the upper end surface of the first sleeve member 4, respectively. .

Next, the fluid dynamic bearing of the second embodiment shown in FIG. 3 in which the minute gap is exaggerated has substantially the same structure as the fluid dynamic bearing of the first embodiment. The difference is the first
It is in the shape of the sleeve member 4. Although the first sleeve member 4 in the second embodiment is a substantially cylindrical member having a thickness as shown in FIG. 6, the upper end surface is different from that in the first embodiment.

That is, in FIG. 3, the first sleeve member 4
The small gap between the upper end surface of the hub 6 and the back surface of the hub 6 is not a simple disk-shaped gap extending horizontally, but a tapered disc-shaped minute gap inclined from the inner periphery to the outer periphery. A labyrinth-like minute gap R5 communicating with the vertical annular minute gap portion is formed. This labyrinth-like minute gap R5
Has one end open to the atmosphere and the other end communicated with the minute gap R1, but the length between the open end to the atmosphere and the minute gap R1 is equal to the length of the capillary gap minute gap of the minute gap R1. By comparison, it is sufficiently long. In FIG. 3, this sufficiently long communication path is realized by forming a substantially conical concave portion 6b on the back surface of the hub 6 and a substantially conical convex portion 4b on the upper end surface of the first sleeve member. .

A substantially conical concave portion 6 formed on the back surface of the hub 6
b and the substantially conical projection 4b formed on the upper end surface of the first sleeve member are both flat surfaces. However, if a dynamic pressure groove is formed on the surface of the substantially conical convex portion 4b,
Radial dynamic pressure and thrust dynamic pressure can be respectively increased. Moreover, by forming the dynamic pressure groove so that the dynamic pressure is generated from the outside to the inside of the bearing, the lubricating oil moves so as to be drawn into the inside of the bearing, which also prevents the leakage of the lubricating oil it can.

Further, the fluid dynamic bearing of the third embodiment shown in FIG. 4 in which the minute gap is exaggerated has substantially the same structure as the fluid dynamic bearing of the first embodiment. The difference is the second
It is in the shape of the sleeve member 5. That is, the second sleeve member 5 in the first embodiment is a cylindrical member having both ends open, and the lower open end is hermetically and liquid-tightly sealed by the disc-shaped lid member 10 to form a one-end open sleeve. However, the second sleeve member 5 in the fourth embodiment is manufactured as a one-end open sleeve from the beginning.

Labyrinth-like minute gap R5 in FIG.
Is basically the same as in the first embodiment. The difference is that the open end to the atmosphere of the labyrinth-like minute gap R5 that is sufficiently long is tapered. This tapered opening end can be realized by providing a tapered notch on the inner peripheral surface of the opening end of the second sleeve member 5, as shown in FIG. This tapered notch may be provided not on the inner peripheral surface of the open end of the second sleeve member 5 but on the opposing surface of the hub 6 opposing it.

Although the three embodiments have been described above, the labyrinth-like minute gap R5 according to the present invention is provided in the hub 6
It goes without saying that other shapes may be used as long as they satisfy the essential condition of being formed between the back surface of the first sleeve member 4 and the thick upper end surface of the first sleeve member 4. Also,
The tapered opening end of the labyrinth-shaped minute gap R5 to the atmosphere communicates the tapered disk-shaped minute gap portion inclined in the outer peripheral direction shown in FIG. 3 with the vertical annular minute gap portion near the outer peripheral portion. It goes without saying that the present invention can be applied not only to the labyrinth-like minute gap R5 described above but also to a labyrinth-like minute gap R5 having another shape. Further, the one-end open type sleeve for receiving the flanged shaft 1 is shown as being constructed by assembling the first sleeve 4 and the second sleeve 5 manufactured separately from each other. Of course, it does not matter.

[0028]

The spindle motor according to the present invention has a flanged shaft formed by pressing a cylindrical member into a ring member, a first sleeve member into which the cylindrical member is inserted, and a second shaft member into which the ring member is inserted. A rotor having a hub is rotatable with respect to a stator by a fluid dynamic pressure bearing composed of a one-end open type sleeve composed of two sleeve members and lubricating oil filled in a minute gap including a bearing gap between these bearing constituent members. , A labyrinth seal portion is formed between a back surface of the hub and an upper end surface of the first sleeve member. Therefore, the length of the capillary seal is sufficiently longer than that of the conventional device, and the lubricating oil does not leak out of the bearing due to the thermal expansion of the lubricating oil, the centrifugal force, and the capillary phenomenon due to fine scratches on the processing surface.

Further, since the labyrinth seal portion is formed between the upper end surface of the first sleeve member of the sleeve and the back surface of the hub, a new member for forming the labyrinth seal portion is unnecessary, and the dynamic pressure bearing or The number of parts of the spindle motor does not increase. Since the length of the capillary seal is sufficient, it is not necessary to provide an oil pad even if an oil repellent is provided. Therefore, the labyrinth seal portion can be formed in accordance with the demand for downsizing of the apparatus and cost reduction.

Further, a labyrinth seal portion is provided in which a dynamic pressure groove is formed on the surface of the substantially conical convex portion of the first sleeve member so as to generate a dynamic pressure from the outside to the inside of the bearing. In the spindle motor, the dynamic pressure in the radial direction and the thrust direction increased, and the leakage of the lubricating oil to the outside due to the dynamic pressure was also attempted.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of one embodiment of a spindle motor according to the present invention.

FIG. 2 is a longitudinal sectional view of the fluid dynamic bearing according to the first embodiment in which a minute gap and the like are exaggerated.

FIG. 3 is a longitudinal sectional view of a fluid dynamic bearing according to a second embodiment in which a minute gap and the like are exaggerated.

FIG. 4 is a longitudinal sectional view of a fluid dynamic pressure bearing according to a third embodiment in which a minute gap and the like are exaggerated.

FIG. 5 is a perspective view of the flanged shaft 1. FIG.

6 is a perspective view of the first sleeve member 4. FIG.

FIG. 7 is a longitudinal sectional view of an example of a conventional spindle motor.

[Explanation of symbols]

 Reference Signs List 1 shaft with flange 2 cylindrical member 3 ring member 4 first sleeve member 4a annular projection 4b substantially conical projection 5 second sleeve member 6 hub 6a annular projection 6b substantially conical recess 6c skirt 7 rotor magnet 8 stator coil 9 Motor substrate 9a Cylindrical part 10 Disc-shaped lid member F Lubricating oil G1 Radial dynamic pressure groove G2 Thrust dynamic pressure groove R1, R2, R3, R4 Micro gap R5 Labyrinth micro gap r1, r2, r3, r4 Groove or hole S taper Annular gap

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H02K 29/00 H02K 29/00 Z (72) Inventor Naoki Kawawada 1-8 Nakase Nakase, Mihama-ku, Chiba-shi, Chiba Inside Seiko Instruments Inc. (72) Hiromitsu Goto 1-8-8 Nakase, Mihama-ku, Chiba-shi, Chiba Prefecture Inside Seiko Instruments Inc. (72) Atsushi Ota 1-8-8 Nakase, Mihama-ku, Chiba-shi, Chiba Inside Instruments Co., Ltd. (72) Inventor Koji Nitori 1-8-1, Nakase, Mihama-ku, Chiba-shi, Chiba Prefecture Inside Seiko Instruments Inc. Company F-term (reference) 3J011 AA04 BA02 BA04 BA08 CA01 CA02 CA04 JA02 KA04 MA03 MA24 5H019 AA00 AA07 AA09 CC04 DD01 EE01 EE14 FF03 5H605 AA02 AA07 BB05 BB19 CC04 EB03 EB06 EB28 EB33 5H607 AA05 BB01 BB09 BB14 BB17 CC01 GG01 GG02 GG01 GG02

Claims (5)

[Claims] 1. A flanged shaft formed by press-fitting a cylindrical member into a ring member, a thick first sleeve member into which the cylindrical member is inserted, and a second sleeve member into which the ring member is inserted. A rotor having a hub is rotatably supported on a stator by a fluid dynamic pressure bearing composed of a one-end open type sleeve and a lubricating oil filled in a minute gap including a bearing gap formed between these bearing components. The spindle motor according to claim 1, wherein a labyrinth seal portion is formed between a back surface of the hub and an upper end surface of the first sleeve member. 2. The labyrinth seal portion is constituted by a minute gap between a downward annular projection formed on the back surface of the hub and an upward annular projection formed on an upper end surface of the first sleeve member. The spindle motor according to claim 1, wherein the spindle motor is a motor. 3. The labyrinth seal portion is constituted by a minute gap between a substantially conical concave portion formed on a back surface of the hub and a substantially conical convex portion formed on an upper end surface of the first sleeve member. The spindle motor according to claim 1, wherein: 4. The spindle motor according to claim 3, wherein a dynamic pressure groove is formed on a surface of said substantially conical convex portion so as to generate a dynamic pressure from the outside to the inside of the bearing. 5. The spindle motor according to claim 1, wherein an opening end of said labyrinth seal portion is tapered.